Orthodontic adhesives serve to fasten an orthodontic appliance on the surface of a tooth.
Orthodontic adhesives typically comprise one or more polymerizable monomers of the acrylate or methacrylate type, together with a polymerization initiator.
An orthodontic appliance is durably fastened to the tooth by causing the monomers present in the adhesive to polymerized, e.g. under irradiation from blue light.
Once the orthodontic treatment has been performed, the orthodontic appliance needs to be removed from the surface of the tooth.
To do that, the appliance can be removed mechanically by using forceps designed for that purpose. That method is relatively rough and can lead to lesions in the enamel. The use of forceps can be painful, or even traumatic for the patient. The adhesive is not necessarily removed in full, and residues may remain on the teeth, thus requiring the use of a dental bur to remove them. That treatment can also lead to additional damage to the enamel.
In order to avoid using that mechanical method for unsticking the orthodontic appliance, application JP 2007/320929 proposes an orthodontic adhesive that incorporates thermo-expandable particles. Each thermo-expandable particle is in the form of a shell encapsulating an expansion agent, such as butane. Under the effect of an increase in temperature, the expansion agent contained in the shell expands, thereby causing the shell to expand and the volume of the particles to increase.
Application JP 2007/320929 proposes performing unsticking, no longer by using forceps, but by heating the adhesive to a temperature that is relatively high in order to expand the thermo-expandable particles, thereby causing the polymer lattice to break. Nevertheless, the use of a heater member applying a relatively high temperature can lead to discomfort, and even to a risk of burning for the patient being treated.
Removing other types of dental adhesive is likewise not possible in a manner that is entirely satisfactory. On this topic, mention may be made of removing dental cements that are used for temporarily plugging a cavity formed inside a tooth, e.g. after removing caries. Such dental cements are usually removed mechanically using a dental bur. That method can lead to damaging a patient's dental tissue.